.geometry "version 0.51";
.l0; 
.text("Construct a triangle given the length L of one
side, the distance D from an adjacent vertex to the
incenter, and the radius r of the incircle.  Adjust
the sizes of the lengths L, D, and r to play with
the figure.", .l0);
v1 = .free(-0.904192, 0.877245);
v2 = .free(-0.10479, 0.877245);
v3 = .free(-0.913174, 0.805389);
v4 = .free(-0.494012, 0.805389);
v5 = .free(-0.904192, 0.721557);
v6 = .free(-0.721557, 0.721557);
l1 = .l.vv(v1, v2, "L");
l2 = .l.vv(v3, v4, "D");
l3 = .l.vv(v5, v6, "r");
v7 = .free(-0.173653, 0.0508982, "A");
c1 = .c.ctrvv(v7, v1, v2, .in);
v8 = .vonc(c1, 0.625749, 0.0508982, "B");
l4 = .l.vv(v7, v8, [.white, .blink, .white], "L");
c2 = .c.ctrvv(v7, v3, v4, [2 .in, .blink, 2 .white, .in, .white]);
l5 = .l.vlperp(v8, l4, .in);
c3 = .c.ctrvv(v8, v5, v6, .in);
v9 = .v.lc(l5, c3, 1, .in);
l6 = .l.vlpar(v9, l4, [3 .in, .blink, .white], .longline);
v10 = .v.lc(l6, c2, 1, [.white, 3 .in, .blink1, .white]);
c4 = .c.ctrvv(v10, v5, v6, [.white, 3 .in, .blink, .white]);
l8 = .l.vc(v7, c4, 2, [5 .in, .blink, .white], .longline);
l9 = .l.vc(v8, c4, 1, [5 .in, .blink, .white], .longline);
v12 = .v.ll(l8, l9, [.white, 4 .in, .blink1, .white], "C");
l10 = .l.vv(v7, v12, [.white, .in]);
l11 = .l.vv(v12, v8, [.white, .in]);
l12 = .l.vv(v7, v10, [.white, .in], "D");
l13 = .l.vlperp(v10, l4, [.white, .in], "r");
.text("Copy the line segment of length L and
call it AB.", .l1);
.text("Draw a circle of radius D around A.  The
center of the incircle must lie somewhere on this
circle.", .l2);
.text("Draw a line parallel to AB a distance r
away from it.  The center of the incircle must lie
on this line.", .l3);
.text("The center of the incircle is at the
intersection of the line and the circle.  Draw the
incircle with radius r centered at this intersection.", .l4);
.text("Draw tangent lines from A and B to the circle.
They will intersect at the point C which is the circle's
third vertex.", .l5);
.text("Press 'Next' to continue ...", .red, .tol4);